The typical fever thermometer employed in institutions, such as hospitals, and by doctors, as well as in homes, is fragle, expensive, time consuming to use and requires sterilization for reuse. Yet, large number of such thermometers are employed daily, particularly in the case of institutions where a large number of patients may require that an attendant individually take the patient's temperature several times a day, with resultant substantial investment in thermometers, consumption of time, and cost of sterilization, as well as in some cases, the hazard of breakage. In practice, the usual thermometer is inserted beneath the tongue and requires a substantial period of time for the mercury or other fluid to expand, and the reading of the temperature, particularly in poor light, is very difficult, so that inevitably, it will frequently occur that an erroneous temperature reading will be made
While electrically operated thermometers are in existance, they are in general erratic and the sensing elements expensive. More particularly, the known electrical thermometers function on the principle involving measuring current flow which varies with the resistance of the sensing element, but the current source and the meters also constitute variables rendering such thermometers inaccurate, particularly, when the source is a battery which is subject to progressive deterioration, so that even an expensive meter cannot accurately indicate temperature.